It is known that house mites, or dust mites, are a source of allergens that not only cause allergies, but also adversely contribute to other pathologies such as asthma. It has also been established that use of allergen control measures is effective in controlling these conditions. Allergen-proof encasing to contain mites to prevent allergen egress has long been used in bedding (e.g., mattresses, pillows, duvets, and bed upholstery).
Encasings are specially designed covers for pillows, mattresses, duvets, comforters, and box springs. They function to block dust mite allergens so that a user does not breathe them in during sleep or use of a bed. Mattress encasings in particular are usually constructed of two pieces of material cut to fit various lengths of mattresses (e.g., twin, double, queen, or king) and joined by at least one seam that runs around the entire middle of the edge of the mattress. Around one end of the mattress encasing (e.g., at the “head” or “foot” of the mattress), the seam is replaced with a zipper that allows the mattress encasing to be put on the bed. Often, mattress encasings also have two more seams around the entire length of the mattress encasing, along both the top and bottom edges of the mattress. The additional seams may be necessary so that the top or center portion of the mattress encasing can be of a different material or fabric than the rest of the mattress encasing, e.g., to provide a fluid-resistant backing on the top portion of the encasing that is not desired on the bottom portion of the encasing. Dust mite allergens, though, escape through seams, and especially through zippers, which have a plurality of openings that exceed the size of dust mite allergens. A typical twin-size mattress encasing has seams on each corner, seams on the perimeter of the encasing, and double seams where the zipper is, e.g., about 24 feet of seams in all.
Usually the encasing is applied to the mattress by standing the mattress on one end and slipping the encasing over the mattress through the open zippered portion. Once the encasing is nearly completely over the mattress, the mattress is laid flat, and the zippered portion is then zipped closed. This is an unwieldy and time-consuming process. Even though allergists recommend that mattress encasings be frequently washed in ultra high temperatures or with an anti-dust mite laundry additive to increase their efficacy, the process for removing and re-applying the mattress encasings to the mattress discourages users from doing so. Additionally, traditional mattress encasings cannot be used with waterbeds or beds with adjustable air chambers, such as that sold under the Select Comfort® brand name by Select Comfort Corporation of Minneapolis, Minn., USA.
To the extent that such encasing comes in direct or indirect (i.e., through the bed sheets or pillowcases) contact with the human body, it is desired that it be pleasant to the touch and be moisture-vapor permeable. For aesthetic as well as for comfort reasons, it is also desirable that the material has a good drape and does not feel stiff. The prior art has variously attempted to solve these problems.
Mattress encasings have been made from a variety of different materials. It is generally desired that the material have a pore size of less than 10 microns so as to prevent allergens present in the mattress from leaking out. For example, one material used for mattress encasings is knit polyester with a polyurethane backing. The polyurethane backing lends a waterproofing characteristic to the mattress encasing. Spunbond/meltblown/spunbond (SMS) polyolefin nonwovens have also been used in mattress and pillow covers, and they do provide a degree of barrier protection to allergens. SMS nonwovens also exhibit excellent air porosity. Very tightly woven fabrics have also been used for mattress encasings, such as, for example, woven polyester or nylon, woven cotton/polyester blends, and even 100% woven cotton. The woven allergen-barrier fabrics of mattress encasings have been woven from continuous natural and/or synthetic filament and/or spun yarns, with various finishes to yield pore sizes less than 10 microns.
Disposable mattress covers have also been used in the art to prevent contamination of mattresses, and also to prevent or control the presence of dust mite allergens from the user. Known disposable mattress covers comprise different materials or structures that are capable of providing a liquid barrier, in addition to providing moisture vapour permeability, preferably air permeability. Such structures or materials can comprise a single layer, or multiple layers laminated together. An exemplary structure comprises thermoplastic microporous films, e.g., laminated to fibrous layers such as nonwoven layers. Additional materials that are suitable for disposable mattress covers are hydrophilic continuous films, also known as “monolithic films.” These materials do not allow the flow of moisture vapor through open pores or apertures in the material. The materials do transfer substantial amounts of moisture vapor through the film by absorbing water on one side of the film where the moisture vapor concentration is higher, and desorbing or evaporating it on the opposite side of the film where the moisture vapour concentration is lower.